import math
x1,y1,x2,y2 = map(float,raw_input().split())
x = x2-x1
y = y2-y1
print math.sqrt(math.pow(x,2)+math.pow(y,2)) import math math x1,y1,x2,y2 = map(float,raw_input().split()) x1 map(float,raw_input().split()) map float raw_input().split() ().split () raw_input split y1 x2 y2 x = x2-x1 x x2-x1 x2 x1 y = y2-y1 y y2-y1 y2 y1 print math.sqrt(math.pow(x,2)+math.pow(y,2)) math.sqrt math sqrt math.pow(x,2)+math.pow(y,2) math.pow(x,2) math.pow math pow x 2 math.pow(y,2) math.pow math pow y 2 y = y2-y1 y2-y1 y x = x2-x1 x2-x1 x y2 = map(float,raw_input().split()) map(float,raw_input().split()) y2 y1,x2,y2 = map(float,raw_input().split()) map(float,raw_input().split()) y1 x1,y1,x2,y2 = map(float,raw_input().split()) map(float,raw_input().split()) x1 x2,y2 = map(float,raw_input().split()) map(float,raw_input().split()) x2
import math
x1,y1,x2,y2 = map(float,raw_input().split())
x = x2-x1
y = y2-y1
print math.sqrt(math.pow(x,2)+math.pow(y,2))